The document discusses the F.I.T.T. principle for exercise - Frequency, Intensity, Time, and Type. It explains each component of the principle: Frequency refers to how many times per week one should exercise; Intensity refers to how hard the body is working during exercise; Time refers to the duration of exercise sessions; Type refers to the kind of physical activity one engages in. Following the F.I.T.T. principle helps to structure an effective exercise routine tailored to one's interests, skills, and limitations.